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Full text of "The manufacture and properties of iron and steel"

224,                       METALLURGY OF IROK ASTD STEEL.
not heat the bath, but cools.it, and as the flame is the only-heating agent, the more rapid the reaction the lower will be the resultant temperature of the bath. The absorption of heat; by the reduction of ore may be, illustrated in a Bessemer converter. The addition of four hundred pounds of ore at the beginning of the blow will have as much cooling effect as one thousand pounds of scrap. It is hardly likely that the,'fusion of the ore takes so;much more heat than the fusion of steel, and the ox}rgen should be a source of heat, as it assists in burning the silicon more quickly and renders unnecessary the admission of a great volume of nitrogen that would enter if air had1 to be supplied. "We are driven to the conclusion that the cooling effect is due to the absorption of energy in the separation of iron from its oxygen. The union of this oxygen with silicon should be a source of heat, but if the silicon is present, it would be burned anyway by'the blast whether the ore is added or not, and therefore, the heat produced by it will be the same in either case, save a certain gain from the absence of nitrogen.
SEC. Xllf.—Ore needed to reduce a bath of • pig-iron.—In the last section it was found that for every ton of pig-iron 500 pounds of ore are needed to oxidize the silicon and carbon, and of this amount 80 pounds will be used in supplying the oxide of iron for the slag; This calculation assumed that the ore was pure Fe203, which is never true, and1 did not allow for the presence of silica from other sources. Every pound of' silica in the charge will claim a certain amount of FeO in order to form a slag, and this calls for an increased amount of ore. It was also assumed that the pig-iron contained one per cent, silicon, and it is necessary to change the figures if there is a different content of this element. No allowance was made for the action of the flame, as the last section was devoted, exclusively to the heat generated or absorbed by an internal reaction. It may be well, therefore, to see how theoretical calculations agree with practical results.
In Section Xllb were given some data on the use of pig-ircin in basic furnaces at Steelton. It was shown, that in. charging 544,430, pounds of pig-iron, most of it' being- cold, the ore used amounted to 144,100 pounds, or 593 pounds per ton,, while with liquid metal' the ore was 643 pounds per ton. This is more than was found by the previous calculation, but there are twot things to be taken into consideration: (1) the action of the flame, (3) the